In related-art, for transmission electron microscope (TEM) sample preparing, photomask repairing, and the like, there has been proposed a method of using a focused ion beam apparatus to irradiate a target position with a focused ion beam to perform processing.
Generally, the focused ion beam apparatus includes an ion source for generating an ion beam, a condenser lens for condensing the ion beam, an aperture for reducing the ion beam diameter, and an objective lens for focusing the ion beam to the target. Generally, an einzel lens is adopted as the condenser lens. The einzel lens includes three electrodes (incident side electrode, intermediate electrode, and exit side electrode) which are arranged along an ion beam irradiation path. The incident side electrode and the exit side electrode are grounded, and a condenser voltage is applied to the intermediate electrode. Further, the focused ion beam apparatus includes an extracting electrode between the ion source and the condenser lens, and an extracting voltage is applied between the ion source and the extracting electrode to extract ions from the ion source.
Recently, in order to further reduce the ion beam diameter, there has been proposed an apparatus in which a bipotential lens is adopted as the condenser lens (for example, see International Patent WO2010/016394). The bipotential lens includes three electrodes (incident side electrode, intermediate electrode, and exit side electrode) which are arranged along an ion beam irradiation path. An extracting voltage is applied between the ion source and the incident side electrode so that the incident side electrode functions as the extracting electrode. Note that, the bipotential lens is similar to the einzel lens in that the condenser voltage is applied to the intermediate electrode, and the exit side electrode is grounded.